1/2 T. H. MORGAN. 



big claw had been lost and a new one of the same kind was re- 

 generating on the same side. Przibram has also described cases 

 of this sort. This result is all the more interesting since in the 

 lobster the big claw is present in some individuals on one side, 

 and in other individuals on the other. It cannot be claimed in 

 the lobster that one kind of claw represents an undeveloped stage 

 of the other. In the regeneration of the claws, as especially well 

 seen in the lobster, the particular type of claw is present, although 

 not always fully developed, at an early stage, as Przibram has de- 

 scribed, and as I have also found. No doubt the advocates of 

 the view that all beneficial processes have been acquired because 

 of the benefit conferred, will find in these cases of transposition of 

 the big claw from one side to the other evidence of the acquire- 

 ment of a useful process through natural selection, but I do not 

 think that there is any connection of this sort in these cases. 1 



I have intimated above that the injury to the blood-vessels 

 that run to the leg may be closely connected with the changes 

 that take place in the leg, and account for the absence of trans- 

 position in those experiments of Wilson's in which the nerve of 

 the small claw was cut (and presumably also the blood-vessel). 

 My work on the fiddler-crab convinced me that cutting the 

 blood-vessels, which seems nearly always to take place when the 

 nerve is cut, brings about important changes in the condition of 

 the leg. If my suggestion prove correct, namely, that the lack 

 of transposition in Wilson's experiment is due to injury to the 

 blood-vessel rather than to cutting the nerve, then it is possible 

 that the whole phenomenon of transposition may be connected 

 with the condition of the blood supply to the leg. After re- 

 moval of the large claw more blood may be thrown into the ves- 

 sel going to the small claw, and this may be the cause of the 

 change that takes place. 



1 In this respect I am in entire agreement with Wilson. 



